DE 37 21 398 A1 describes a conveying assembly composed of a pump with a drive device, the pump being surrounded on all sides by a pump casing which has a suction space with an intake port and a pressure space with an outlet port. The pump casing is designed to be water-tight and is connected to a motor casing which is likewise designed to be water-tight, receives the drive device and encloses a motor space which surrounds the encapsulated drive unit and is divided off, liquid-tight, with respect to the suction space. The motor space is filled with a barrier medium, in this case with oil, which serves for lubricating the bearings, any gearwheels or the like and acts upon the seals and discharges the heat via the motor casing into its surroundings. Such underwater conveying devices are used in the ocean for the conveyance of hydrocarbons.
In crude oil and natural gas production in the ocean, deposits are being developed at ever greater water depths, in this context water depths of up to 4000 m are not uncommon. Correspondingly, the pipeline systems and conveying assemblies also have to fulfill increasingly stringent requirements in respect of resistance to hydrostatic pressures from outside, caused by the water column, and from inside, caused by the reservoir pressure of the crude oil and natural gas. Usually, pipeline systems for deep-sea conveyance are designed for an internal excess pressure of 300 to 500 bar and have to withstand an external excess pressure of up to 400 bar depending on the water depth.
Additional challenges are that the temperatures of the surrounding water and those of the conveyor process medium are different, thus, while the water temperature lies between 1 and 4° C., the temperature of the process medium will rise to above 100° C., so that correspondingly high thermal loads occur, and also the formation of ice has to be taken into account in the case of gas hydrates. All the components integrated into a conveying system must be capable of withstanding at least the loads set out above.
Pump systems for the deep-sea conveyance of hydrocarbons are usually designed such that the pump and the drive device, such as a motor and clutch, are installed in a common casing. It is thereby possible to dispense with a technically critical shaft leadthrough from the pump casing to the motor casing. In this case, there is a region filled by the process medium, to be precise the suction space, the conveying chambers of the pump and the pressure space, and there is a region not filled by the process medium, with the motor, bearing and clutch. The two regions are separated from one another by a shaft seal; the region not filled with the process medium, with the motor, bearing and clutch space, is filled with a barrier medium, usually with water or oil.
The joint conveyance of crude oil and natural gas means that liquids and gases are transported next to one another. In crude oil/natural gas conveyance, a multiphase mixture, as it is known, is conveyed, where there is a high likelihood of the temporary presence of only one phase, that is to say only liquids or only gaseous components are conveyed for considerable periods of time. Furthermore, the composition of the multiphase mixture fluctuates over a wide range and over relatively long periods of time, and therefore pump technology has to fulfill special requirements here.
If hydrocarbons emerge in an uncontrolled way, it is necessary to intercept these as near to the outlet point and as completely as possible, in order to reduce or avoid environmental pollution and intercept the emerging conveyable or process medium as completely as possible.
DE 10 2008 018 407 A1 describes a generic underwater conveying assembly in which a pressure casing is filled with the process medium and surrounds the module which is combined in a module casing.
DE 100 81 956 T1 describes a vibratory pump having a frame group with a drive solenoid accommodated in the frame group. A transmission group with an element oscillating axially with respect to the frame group is provided, the oscillating element being attached with one end to the drive solenoid. The pump is designed as a submersible pump with an inlet arranged at the lower end on the end face. The medium to be conveyed is conveyed through a passage resembling an annular gap to the pump outlet via an auxiliary pump chamber and pump outlets emanating from the latter. Such a pump is preferably provided as a shaft pump. An attachment with a cylindrical upper portion and with a lower conical portion which has water inlet ports is provided so that the pump can be used as a suction pump. Use at great depths or for the conveyance of hydrocarbons is not provided or is not possible.